Snap mechanism for slow-break electric switches



Aug. 30, 1966 D. W. JOHNSON 3,270,157

SNAP MECHANISM FOR SLOW-BREAK ELECTRIC SWITCHES Filed Sept. 24, 1964INVENTOR.

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United States Patent C) 3,270,157 SNAP MECHANISM FOR SLOW-BREAK ELECTRICSWITCHES David W. Johnson, Newington, Conn., assignor to The Arrow-Hart& Hegeman Electric Company, Hartford, Conn., a corporation ofConnecticut Filed Sept. 24, 1964, Ser. No. 398,999 2 Claims. (Cl.200-67) This invention relates to electric switches. More particularly,it relates to overcenter switch mechanisms which act with a snap actionto cause engagement and disengagement of switch contacts.

Heretofore, switch mechanisms have been known for use in A.C. circuitsfor opening switch contacts an optimum distance by what is known as aslow-break. In such devices, an operating member lwas moved between twopositions, but it could be held in inbetween positions in which themovable and iixed contacts were neither fully engaged nor fullyseparated. In such intermediate positions, the contact pressure was notsuicient for firm contact and the contacts could overheat, ora small arccould develop, damaging the contacts in either case. Hence, the abilityto tease these switches was undesirable.

For many years, overcenter switch mechanisms have been used to snap amovable contact from one position to another, but the movable contactmember commonly moved as a unit with overcenter operated member. Theseswitches, beside being relatively expensive, did not possess theadvantage of the slow break, optimum-contact separation features.

In recent years, increased horsepower ratings and needs for switcheswith a longer life required a re-evaluation of the switch structure inthe light of the new and heavier duties, such switches are required toperform, such as in connection with floor polishers and otherappliances. Manufacturers of such appliances demanded a switch structurewhich would perform satisfactorily for upwards of 100,000 cycles oroperations.

Therefore, it is an object of this invention to provide an improvedswitch mechanism embodying advantages heretofore available in only oneor another types of prior switches, which improved mechanism will becapable of greatly increased life and yet can be made and sold atcompetitive prices.

Another object of the invention is to provide a switch mechanismembodying the advantages of movement of the movable contact from oneposition to another independent of the handle or operating member, incombination with slow-break, optimum contact separation features.

Other objects and advantages will appear as the invention is describedin connection with the accompanying drawing.

In `the drawing:

FIG. l is la longitudinal section view through a switch embodying theinvention, showing the switch in opencircuit position.

FIG. 2 is a View similar to FIG. 1, but with the contacts inclosed-circuit position.

FIG. 3 is an exploded view showing in perspective the operating button,the operating member and yoke member.

Referring to the drawing, the parts may be housed in a casing,preferably of generally rectangular shape having coperating top andbottom parts such as hollowed out base and an internally recessed cover12 molded from insulating material.

One or two pairs of fixed and movable contacts may be provided, eachpair being located along one longitudi- ICE nal casing wall. Fixedcontact 14 may be conveniently stamped from sheet metal and may have acontact button 14e affixed in downwardly facing direction to anoverhanging arm 14a of the contact. The contact may also be providedwith a conventional terminal portion 14t accessible from the outside ofthe base for connection of conductor wires, as usual.

The movable contact 16 may be stamped from thin flexible sheet metal asa long narrow strip having la button 16C on one end adapted to engageand disengage the xed contact button 14a` as the movable Contact 16 isoperated. The opposite end of the movable contact is axed to a terminalmember 18 stamped conventionally from sheet metal and having a portionaccessible from the outside of the casing for connection of conductorwires, as usual. The movable contact is normally biased towardengagement with the fixed contact 14C.

To move the movable contact 16 against its bias and away from the fixedcontact 14e` and also to allow the movable contact to engage the fixedcontact, a swingable yoke member designated generally by the numeral 20is provided.

The yoke may be lformed of tough ilexible synthetic insulating material,such as nylon, in generally U-shape with oppositely out-turned feet 23and 24 at the ends of its parallel arms 21 and 22 and may have axiallyaligned cylindrical trunnions 25 and 26 extending beyond the ends ofsaid feet for pivotally supporting the yoke. The trunnions may be seatedin opposite bearing notches or recesses 25u formed in the sides of thebase 10 at or near the top edges of said sides. To move the movablecontact against the bias in order to disengage xed :and movablecontacts, cam surfaces 27 are formed on the inner or under surfaces ofeach of the feet 23 and 24 of the yoke 20.

To swing the yoke 20 between two opposed positions a coiled compressionspring 28 is provided which arts with an overcenter action to snap theyoke between its two positions, as the line of action of the spring isswung through its overcenter position in known fashion. The spring maybe seated at one end on a nub 29 formed in the transverse portion of theyoke. The opposite end o the spring seats against tan-d engages with afinger 32 formed on an actuating member 30.

The spring actuating member may be of any convenient shape with a pivotpin 34 passing transversely therethrough adapted to seat in bearingrecesses 36 formed in the cover 12. The cover 12 is recessed orapertured centrally to receive the portion of the operating memberlocated above the pivot 34. For actuating the operating member 30, anarm 38 is directed radially from the pivotal axis of the operatingmember toward a recess 42, formed in an operating button which isreciprocable between depressed and elevated positions.

The operating buttom-member designated generally by the numeral 40 isslidably mounted in the casing. The buttom member is preferably formedor molded from insulating material into the form best illustrated inFIG. 3 with a main body portion 41 from which upwardly extends acylindrical button portion 44 adapted to be operated manually or by footpressure.

The button portion extends through an aperture in the cover 12. To guidethe movement of the button in a rectilinear path, a leg 46 extendsdownwardly or inwardly from the body of the button member and slidablytits within a Irecess or well 47 formed in the base of the casing.Preferably the leg and guide recess will be rectangular or non-circularin cross section to prevent the buttom member from rotating about i-tsvertical axis.

The button-member 40 is normally pressed upwardly or outwardly of thecasing by a coiled compression spring 48 seated in a well or bore 49 inthe base of the casing and pressing at its lower end upon the bottom ofthe bore 49 and at its top against the body portion 41 of thebutton-member. The button-member is kept from being pressed out of thecasing by shoulders 43 on the body portion engaging the inner surface ofthe cover 12 adjacent the circular aperture through which the buttonportion 44 of the button-member extends.

It will thus be seen that when the button is in normal positon, it iselevated by the bias of the spring 48. In such position, the partsoccupy the positions illustrated in FIG. l wherein the actuating member30 is tilted With the linger 32 inclined to the left in what may becalled the seven oclock position. The yoke 20 is thus biased by theovercenter spring 28 into the position where the high point 27h of thecam surface 27 presses the movable contact 16 downwardly to causedisengagement of the movable contact button 16e from the fixed contactbutton 14C.

When the button is depressed, the actuating member 30 is moved to theposition shown in FIG. 2 by reason of the counterclockwise rotationthereof caused by engagement of the arm 38 with the Walls of recess 42in the button-member 40. Such counterclockwise movement causesovercenter action of the overcenter spring and snaps the yoke 20 fromthe position of FIG. 1 to the position of FIG. 2. This causes the camsurface to be substantialy parallel to the top and bottom surfaces ofthe casing or, in other words, horizontal as viewed in FIG. 2. Suchmovement of the cam surface permits the movable Contact 16 -to moveupwardly under its normal bias and to engage the fixed contact button14C.

It will be noted that the amount of movement permitted the movablecontact with respect to the ixed contact is certain and can bepredetermined so that the movable and fixed contacts will separate theoptimum distance for most effective arc-quenching.

Moreover, movement between `open and closed positions of the contacts,although it is initiated by movement of the operating button 40 isnevertheless free of and independent from movement of the ope-ratingbutton once the `overcenter spring has passed through its overcenterposition. It is not possible, therefore, to tease the movable contact orto hold the movable contact in an intermediate position or in anyposition inbetween its normal on and normal oft positons. This preventsthe operator of the switch from interfering with the proper opening andclosing movements of the contact or maintaining it between the normalopen and closed posi- 4 tions wherein arcing, overheating and otherdeleterious effects could take place.

Furthermore, the opening and closing movement of fthe switch contact 16is relatively slow in spite of the fact a fast-moving overcentermechanism causes such movement. This is due to the camming action of theyoke acting on the contact. As the cam surface wipes over the movablecontact strip 16, in an arc, only the component of such action which isperpendicular to the surface of the contact strip acts to move thecontact button 16a` away from contact 14C.

Modifications within the scope of the invention will occur to thoseskilled in the art. Therefore, the invention is not limited to thespecific form and detail of the parts as illustrated and described.

What is claimed is:

1. In an electric switch, a housing, fixed contact means mounted in saidhousing, a exible metallic strip forming movable contact meansengageable with and disengageable from said fixed contact means, apivoted yoke member, an operating member, overcenter-spring meansengaged with said yoke member and said operating member to swing saidyoke member between two at-rest positions with a snap action as saidoperating member is moved, cam means on said yoke engaging said movablecontact strip and causing movement of said movable contact strip as saidyoke member swings, final movement of the contact means into saidat-rest positions being free of' control by said operating member, saidcam means being formed to move said movable Contact means at a slowerrate of speed than said yoke, so as to provide a slow breakcontact-separating movement.

2. An electric switch as claimed in claim 1 having means pivotallymounting said operating member, and a manually operable member engagingwith said pivoted operating member, and means mounting said manualmember in said housing for rectilinear movement.

References Cited by the Examiner UNITED STATES PATENTS 2,407,378 9/19'46Miller et al. 2,623,960 12/1952 Haydon. 2,725,438 11/ 1955 Bentley.2,881,292 4/ 1959 Winter et al.

ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, Examiner.

D. SMITH, IR., Assistant Examiner.

1. IN AN ELECTRIC SWITCH, A HOUSING, FIXED CONTACT MEANS MOUNTED IN SAID HOUSING, A FLEXIBLE METALLIC STRIP FORMING MOVABLE CONTACT MEANS ENGAGEABLE WITH AND DISENGAGEABLE FROM SAID FIXED CONTACT MEANS, A PIVOTED YOKE MEMBER, AN OPERATING MEMBER, OVERCENTER-SPRING MEANS ENGAGED WITH SAID YOKE MEMBER AND SAID OPENING MEMBER TO SWING SAID YOKE MEMBER BETWEEN TWO AT-REST POSITIONS WITH A SNAP ACTION AS SAID OPERATING MEMBER IS MOVED, CAM MEANS ON SAID YOKE ENGAGING SAID MOVABLE CONTACT STRIP AND CAUSING MOVEMENT OF SAID MOVABLE CONTACT STRIP AS SAID YOKE MEMBER SWINGS, FINAL MOVEMENT OF THE CONTACT MEANS INTO SAID AT-REST POSITIONS BEING FREE OF CONTROL BY SAID OPERATING MEMBER, SAID CAM MEANS BEING FORMED TO MOVE SAID MOVABLE CONTACT MEANS AT A SLOWER RATE OF SPEED THAN SAID YOKE, SO AS TO PROVIDE A SLOW BREAK CONTACT-SEPARATING MOVEMENT. 